A highly sustainable hydrothermal synthesized MnO2 as cathodic catalyst in solar photocatalytic fuel cell

A unidirectional flow solar photocatalytic fuel cell (PFC) was successfully developed for the first time to offer alternative for electricity generation and simultaneous wastewater treatment. This study was focused on the synthesis of alpha-, delta- and beta-MnO2 by wet chemical hydrothermal method for application as the cathodic catalyst in PFC. The crystallographic evolution was performed by varying the ratios of KMnO4 to MnSO4. The mechanism of the PFC with the MnO2/C as cathode was also discussed. Results showed that the catalytic activity of MnO2/C cathode was mainly predominated by their crystallographic structures which included Mn-O bond strength and tunnel size, following order of alpha- > delta- > beta-MnO2/C. Interestingly, it was discovered that the specific surface areas (S-BET) of different crystal phases did not give an impact on the PFC performance. However, the P-max could be significantly influenced by the micropore surface area (S-micro) in the comparison among alpha-MnO2. Furthermore, the morphological transformation carried out by altering the hydrothermal duration demonstrated that the nanowire alpha-M3(24 h)/C with 1:1 ratio of KMnO4 and MnSO4 yielded excellent PFC performance with a P-max of 2.8680 mW cm(-2) and the lowest R-int of 700 Omega. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A unidirectional flow solar photocatalytic fuel cell (PFC) was successfully developed using different MnO2 crystal phases as cathodic catalysts, demonstrating the significant influence of crystallographic structures on catalytic activity. Micropore surface area was found to impact PFC performance, with nanowire alpha-M3(24 h)/C material showing the best performance.